Production of biofuel from renewable processes is a key step towards securing a more responsible energy economy for the future. But beyond this, these fuels must be used in way that does not generate, or minimises, harmful emissions such as carbon dioxide.
Many important advances in biofuel production have been made. However, while advances in commercial production of algae has made great leaps regarding species selection, growth media, and even genetic manipulation, there remains a disproportionate lack of advance in the areas relating to working algal pond depth and harvesting. Algal pond depth is restricted by limited penetration of sunlight into the pond. Efficient harvesting of large quantities of algae requires large expenditures of energy and money.
Closed bioreactors are one means to overcome some of these disadvantages. However, such bioreactors are severely limited by cost and infrastructure requirements especially for biofuel applications. Open ponds are much more economic, particularly for cultivating algae, but are often is restricted by the availability of light to specific dimensions within the algal ponds. That is, light may only penetrate to a certain depth leaving many algae with sub-optimal illumination for growth, or even no light for growth.
In addition most algae growing systems, e.g. closed bioreactors or open ponds, experience photo-inhibition caused by over exposure to sunlight levels at the water surface. In an open pond this occurs a within the first few centimeters of water where little algae growth results. Only after the incoming sunlight intensity has been greatly reduced by the absorbance of photo-inhibited algae at the surface, do algae begin to grow at intermediate depths.
Furthermore, algae depend on photosynthetic pigments, such as chlorophyll, that selectively absorb certain wavelengths of light while other wavelengths are of lesser use, thus further reducing the overall utility of incoming solar radiation. As a result, algae systems exhibit low solar-photosynthetic efficiency. By most estimates, the photosynthetic efficiencies of current algae bioreactor systems average between 2% to 7% and have a maximum theoretical yield of 11% solar-photosynthetic efficiency.
Therefore, there is a need for an improved bioreactor that addresses the disadvantages of previous bioreactors with respect to bioreactor design, cost, and the inherent biological incompatibilities between the available light in such bioreactors and the algal photosynthetic system.
It is to be understood that any reference herein to prior art does not constitute an admission that such art forms a part of the common general knowledge in the art, in Australia or any other country.